Wireless networks for mobile communications include such examples as cellular telephone networks, broadband Personal Communication Services (PCS), wireless wide-area networks (WANs), wireless local-area networks (LANs), satellite communication systems, and two-way radio systems. These networks include mobile stations that may be telephone or radio handsets, vehicle-based transceivers, wireless data modems, or even semi-fixed units such as wireless local loop (WLL) stations. Many such networks also have an infrastructure including one or more base station units or access points whose locations are fixed and which communicate with the mobile stations and possibly also with each other and/or an external network. In a cellular telephone network, for example, the base station units provide an interface between the mobile stations and the public switched telephone network, communicate with registries to perform authentication, authorization and billing functions, and may also interact with each other to perform call management and handoff functions.
Certain wireless networks for mobile communications are augmented by adding the capability to locate the position of a particular mobile station. The Federal Communications Commission regulation (Docket No. 94-102, Third Report and Order adopted Sep. 15, 1999, released Oct. 6, 1999) requires all cellular carriers in the United States to be able to locate the position of a cellular telephone utilizing a handset-based technology making a 911 call within 50 meters for 67 percent of calls and within 150 meters for 95 percent of calls. Other uses for position location services include value-added user features such as mapping, routing and navigation and vehicle fleet management support.
Several different approaches for position location may be implemented. For example, terrestrial methods, satellite positioning system (SPS) methods, and hybrids of terrestrial and satellite-based methods may be utilized. One such satellite positioning system is the well-known Global Positioning System (GPS), which is a “constellation” of 24 well-spaced satellites that orbit the earth. The precise positions of the GPS satellites can be determined from different sets of information transmitted by the satellites themselves. Terrestial systems, such as cellular communication systems, utilize base stations of known locations that transmit signals.
The amount of time required for the signals to travel from the satellites or base station transmitters to the mobile station may be measured and used to compute the distances (or ranges) between the transmitters and the mobile station. From these distances and the known locations of the transmitters, the location of the mobile station can be determined.
The Telecommunications Industry Association (TIA) has promulgated a recommended standard for the implementation of Location Services Enhancements for use in Wireless Radiotelephone Service. (TIA TR-45.2 PN-4747 Location Services Enhancements, Nov. 18, 2002, to be published as TIA/EIA/IS-881). The TIA Location Services Enhancements standard specifies intersystem operations to enable a wireless network to provide enhanced location services.
The TIA Location Services Enhancements standard sets forth guidelines for allowing a location services (LCS) client to specify the quality of service (QoS) required for location related tasks. The LCS client is defined as entity which interacts with a wireless network for the purpose of obtaining location information for one or more mobile stations within a set of parameters, such as location QoS (LQoS) parameters. The TIA Location Services Enhancements standard also sets forth proposed ways to prevent the location determination from taking place if the LQoS cannot be met. The TIA Location Services Enhancements standard additionally sets forth that a position estimate may not be returned to the LCS client if the position estimate does not meet the requested LQoS.
Wireless networks, wireless network operators and/or service providers may choose to provide many different types of location services and may deploy various selected technologies to support these services. Unfortunately, there are presently no means to indicate the quality of an available location service to the user of a mobile station. In fact, there is currently no means to indicate to the user whether location services are even available. Therefore, unless there is a mandate or a global decision to support certain types of location services, a mobile user roaming to a different network may not know whether location services are available and supported by a visited network or the quality of the location service that may be available and supported at a particular geographic location and time, be that in a home or visited wireless network.
There is therefore a need in the art for a method, apparatus, and machine-readable medium to provide an indication of location service availability and the quality of the available location service.